Epson Stylus C 60 Service Manual page 43

EPSON Stylus C60
+42VDC +5VDC
IC51
+5V Regulator
R92,R93,Q91,ZD51
+42VDC Line
Constant
Control
C51
Smoothing
Circuit
D51
TRANS(T1)
C11
Smoothing
Circuit
Over Current
Protection
F1,TH1
AC Input
Figure 2-16. C417 PSB/PSE board block diagram
The C417 PSB/PSE board has the various control circuits to stop voltage output if a
malfunction occurs on the power supply board or the main board while the printer
mechanism is on duty. Following explains each control and protection circuit.
Operating Principles
PSC Signal from
Main board
ZD53
+5VDC Line
Over Voltage
Limitation
ZD52,87
+42VDC Line
Over Voltage
ZD91
Limitation
+42VDC Line
Drop Limitation
C84,Q84
Power Drop
Delay Circuit
PC1
Photo Coupler
Q1 Q2,Q31,Q32,Q33
Main Switching Abnormally Feed
Circuit back circuit
Full Wave
Filter Circuit
Rectifier circuit
L1,C1
DB1
Electrical Circuit Operating Principles
1. Regardless of the state of the power switch (On or OFF), the voltage is always
applied to the primary side of the power supply board from the moment or at the
state that AC-plug is plugged in. At this time, F1 plays a role of preventing
AC100V from coming into the F1.
L1 also prevents high harmonic wave noise generated in the RC circuit filter
which consists of C1 from going out, and eliminates the noise from outside here.
2. The AC is full-wave rectified by the diode bridge DB1, and converted to
AC in voltage by the smoothing electrolytic capacitor C11.
3. The pressured up direct current turns Q1 on through the starting resistor R31 and
starts the primary side of the circuit.
4. When the primary side is On, the energy (current) led by the electromagnetic
induction through the trans (T1) does not flow to the secondary side since the
diode (D51) on the secondary side is installed in the opposite direction.
5. When the energy which is charged in the trans is reaching the saturated state, the
voltage which makes Q1 on becomes weak gradually. At the point that this voltage
drops at the certain voltage, C13 absorbs the current in the opposite direction and
Q1 is quickly shut off by the resulting sharp drop.
6. When the primary side is turned off, the energy charged in the T1 is opened
according to the diode (D51) direction which is installed on the secondary side.
Basically, 42 V DC is output by these circuit operations and the number of T1
spiral coil.
7. +5VDC is generated by pressured down this +42VDC as power supply. IC51
pressures down the +42VDC and generates precise +5VDC by chopping off the
output, forming the standard santooth wave form by the outer RC integration
circuit.
The C417 PSB/PSE board has the various control circuits to stop voltage output if a
malfunction occurs on the power supply board or the main board or while the printer
mechanism is on duty. Following explains each control and protection circuit.
+42V line constant voltage control circuit :
The output voltage level of the +42V line is monitored by R92, R93, Q91 and
ZD51. When +42V line reaches about +42.8V, PC1 starts the operation via Q91.
Consequently, FET Q1 switching operation is controlled by this circuit to stabilize
the +42V line.
Revision A
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